MOLECULAR-CLONING AND ANALYSIS OF THE EXPRESSION OF THE E1-BETA SUBUNIT OF BRANCHED-CHAIN ALPHA-KETOACID DEHYDROGENASE IN MICE

The cDNA sequence encoding the murine liver E1 beta subunit of the branched-chain alpha-ketoacid dehydrogenase complex (BCKAD) was determined. In the region encoding the mature E1 beta subunit protein, both the nucleotide composition and predicted amino acid sequence are highly conserved between murine, rat, human, and bovine species. In contrast, they are less well conserved in the 5' sequence encoding the amino terminal preprotein sequence and 3' untranslated region. The pattern of tissue-specific expression of three BCKAD subunit RNAs was determined to be similar in both rat and murine tissues except for that observed in murine liver, where a higher than expected level of E1 beta subunit RNA was observed. Variation in the levels of this subunit might play a major role in the regulation of the overall ability of the murine liver to modulate BCKAD content in response to changing physiologic needs.